The heat exchanger is widely used in various fields. A conventional heat exchanger generally has a flat and rectangular shape of so-called parallel flow type. In order to improve the heat exchange performance to meet different requirements of application and installation, a bent heat exchanger is proposed.
Due to the presence of the fins at the bent position, the heat exchanger is difficult to bend during manufacturing, the bending radius must be large, the bending angle is limited, and the installation space occupied by the heat exchanger is large. In addition, the fins at the bent position tend to be distorted, thus influencing the heat exchange performance, the water drainage performance and the appearance of the heat exchanger, and water may be blown out of or dropped into a pipe system.
For these issues, it is proposed that no fins are interposed at the bent position of the heat exchanger, that is, no fins are interposed between adjacent bent segments of the tubes, so that the bent segments of tubes are also called a segment without fins.
However, because the segments without fins do not participate in heat exchange, if the segments without fins are too long, the effective heat exchange area may be reduced, thus affecting the heat exchange performance. If the segments without fins are too short, the bending radius of the bent segments must be large, the bending angle is limited, and the installation space should be large, thus affecting the heat exchange performance, the water drainage performance and the appearance of the heat exchanger.
Moreover, for the conventional heat exchanger, the influence of bending upon the tubes is usually not taken into account when bending the tubes. The larger the stretching amount of the outer surface of the bent segments of the heat exchanger, the thinner the outer wall of the tube is, therefore, the bursting strength and the corrosion resistance of the tubes are decreased, thus shortening the life of the heat exchanger.